loss of a
This is the plane that was damaged beyond repair as result of an accident, a criminal act or a non-operational occurrence (hangar fire, hurricanes etc.).

worst accident involving a (at the time)
When the accident happened it was, at the time, the worst accident involving a . This includes crashes as a result of criminal acts (shoot down, sabotage etc.) and does also include ground fatalities.

worst accident involving a (currently)
Currently this is the worst accident involving a . This includes crashes as a result of criminal acts (shoot down, sabotage etc.) and does also include ground fatalities.

worst accident in (at the time)
When the accident happened it was, at the time, the worst accident in . This includes crashes as a result of criminal acts (shoot down, sabotage etc.) and does also include ground fatalities.
Please note that accidents that have occurred more than 12 miles / 19,3 km offshore in open waters are classified under one of the three Oceans (Atlantic, Indian, Pacific).

worst accident in (currently)
Currently this is the worst accident in . This includes crashes as a result of criminal acts (shoot down, sabotage etc.) and does also include ground fatalities.
Please note that accidents that have occurred more than 12 miles / 19,3 km offshore in open waters are classified under one of the three Oceans (Atlantic, Indian, Pacific).